That CSF F2-isoP concentrations, F4-neuroP concentrations, or both may be quantitative biomarkers of oxidative damage to brain in Alzheimer's Disease (AD). SPECIFIC AIMS: (1)To determine the specificity of elevated CAF F2-isoP and F4-neuroP concentrations for AD versus other age-related dementing illnesses (Pursuit of this aim does not involve the CRC). (2)To determine if F2-isoP and F4-neuroP concentrations in CSF from living patients correlate w/measures of AD severity, progression, and response to therapeutics.